Apparatus for and method of forming long tangent elbows



March 24, 1970 M. E. REMUS ET AL 3,501,939

APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS Filed Sept. 15,1967 2 Sheets-Sheet 1 46 Inveniora mewmzffiems,

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APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS Filed Sept. 15,1967 March 24, 1970 us ET AL 2 Sheets-Sheet 2 United States Patent O3,501,939 APPARATUS FOR AND METHOD OF FORMING LONG TANGENT ELBOWS MelvinE. Remus, Park Ridge, and Joseph F. Staroba, Des Plaines, Ill.,assignors to Taylor Forge Inc., Bellwood, III., a corporation ofIllinois Filed Sept. 13, 1967, Ser. No. 667,502 Int. Cl. B21d 22/00 US.Cl. 72-343 8 Claims ABSTRACT OF THE DISCLOSURE A die having an arcuatecavity of circular cross section, and an arcuate mandrel of circularcross section disposed in the cavity in radially spaced relation. Oneend of a tubular blank is forced through the cavity and about themandrel whereby to form an elbow at the end of the tubular blank toproduce a long tangent elbow.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates generally to the forming of pipe and more particularly toapparatus for and a method of cold forming an elbow at one end of atubular blank to produce a long tangent elbow.

Description of the prior art Heretofore, various techniques have beenproposed for forming a tubular blank into an elbow. Apparatus of theprior art has in general comprised a die with an arcuate cavity, and anarticulated mandrel extending into the cavity concentrically thereof. Toform an elbow, a short tubular blank, while hot or in some cases cold,is forced lengthwise into the arcuate cavity and over the mandrel.

Elbows formed in the foregoing manner have a number of shortcomings.There occurs undesirable thinning in various portions of the elbow wall;there is a considerable variation in wall thickness throughout theelbow; and there is a substantial differential in thickness at thecrotch and back wall of the elbow relative to the remaining wall areas.Furthermore, the techniques of the prior art, not only are deficient inregard to the forming of conventional elbows, but also are not readilyadaptable to the forming of long tangent elbows.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided a die having an arcuate cavity of circular cross sectionpresenting an entrance and an exit. An arcuate mandrel of circular crosssection is disposed in the cavity with one end terminating at theentrance and with the other end extending outwardly of the exit. Themandrel is allowed to float in the die cavity, but is prevented frombeing ejected, and is positioned lengthwise of the cavity, by means ofreaction means which is spaced from the die and is engaged by the otherend of the mandrel.

Preferably, ring members are disposed loosely in the cavity about themandrel for positioning the latter radially, the radius of curvature ofthe centerline of the mandrel is greater than the radius of curvature ofthe centerline of the cavity, the diameter of the cavity increasesslightly from the entrance to the exit, guide means projects from thedie and is formed with a cylindrical bore that communicates with theentrance end of the cavity, and a cylindrical mandrel extension isdisposed in the bore and has one end engaging the one end of the arcuatemandrel.

In operation, one end portion of a tubular blank is moved lengthwisethrough the cylindrical bore and over the cylindrical mandrel, and isthen forced through the arcuate cavity and over the arcuate mandrelduring which time the ring members are pushed outwardly of the exit endof the cavity. In this manner, an elbow is formed at one end of thetubular blank to produce a long tangent elbow. To complete theoperation, the cylindrical mandrel is removed from the tangent and bore,the reaction means is removed, the arcuate mandrel is forced out of theelbow, and the resultant long tangent elbow is removed from the die andcylindrical bore.

As contrasted with prior art techniques, the apparatus and method of thepresent invention are especially adapted for forming or producing longtangent elbows. Also, with regard to the elbow portions of long tangentelbows formed in accordance with the present invention, thinning of thewall areas is minimized, greater uniformity in wall thickness isattained, and the differential in wall thickness at the crotch and backwall is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an elevational view of adie assembly incorporating the principles of the present invention;

FIGURE 2 is a plan view of the die assembly of FIGURE 1;

FIGURE 3 is a sectional view, taken substantially along the line 3-3 inFIGURE 2, looking in the direction indicated by the arrows, and shows atubular blank in position for forming; and

FIGURE 4 is a sectional view, corresponding generally to FIGURE 3, butshows the blank after it has been formed into a long tangent elbow.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,there is indicated generally by the reference numeral 10 a die assemblywhich includes a main die 12 and a die extension 14.

The die 12 comprises two opposed sections 16 and 18 which are providedwith appropriately formed recesses that together serve to define anarcuate cavity 20 of circular cross section. The cavity 20 presents anentrance 22 opening through one side of the die, and an exit 24 with aflared mouth portion 26 opening through a second side of the die 12. Thediameter of the cavity 20 preferably increases slightlyin the order of.001 inch per inch of length of the axis of the cavity 20from theentrance 22 to the exit 24. The die sections 16 and 18 are securedtogether in a conventional manner, either by bolts or by quick releaseclamp means, with the mating faces of the die sections lying in theplane of the centerline of the cavity 20.

The die extension 14 is in the form of a guide sleeve 28 having acylindrical bore 30 with a diameter corresponding to that of the cavity20 at the entrance 22. The sleeve 28 is provided with a flange 32 whichis secured to the die 12, either by bolts 34 or by quick release clampmeans, with the bore 30 communicating at one end with the cavityentrance 22. If desired, the die extension 14 may be split lengthwiseinto two parts, and each part may be formed integrally with therespective die sections 16 and 18.

Disposed in the cavity 20 is an arcuate mandrel or horn 36 adapted to bepositioned with one end terminating at the entrance 22 and with theother end extending outwardly of the exit 24. The radius of curvature ofthe centerline of the mandrel 36 is greater than the radius of curvatureof the centerline of the cavity 20, and the difference in radii ofcurvatures is about A inch for a cavity of 3 /2 inches in diameter. Acylindrical mandrel extension 38 is disposed in the bore 30. One end ofthe mandrel extension 38 engages the end of the mandrel 36 at theentrance 22 and is centered thereon by a central axial projection 40that seats in a recess 42 in the mandrel 36. The mandrel extension 38 isallowed to tip, swivel or float relative to the mandrel 36, and theouter end is bevelled as at 44.

Arranged about the die 12 is a yoke assembly 46 comprised of a frontreaction bar or plate 48, a rear bar or plate 50, spacer blocks 52, andtie-bolts 54 extending between and through the ends of the bars 48 and50. The yoke assembly 46 is clamped about the die 12 and secured inposition by nuts 56 threaded onto the ends of the tiebolts 54. Inclamped position, the front reaction bar 48 is spaced from the exit 24of the die 12 by the spacer blocks 52, and is engaged by the end of themandrel 36 which extends outwardly of the exit 24. Thus, while themandrel 36 is allowed to float in the cavity 20, it is prevented frombeing ejected, and is positioned lengthwise of the cavity, by means ofthe reaction bar 48. Also, ring members 58 and 60 (FIGURE 3) arepreferably arranged loosely in the cavity 20 about the mandrel 36 forinitially positioning the latter radially.

The above described die assembly is adapted to be positioned on the base62, and beneath the ram 64, of a hydraulic press or the like. In forminga long tangent elbow, a tubular blank is prepared by cutting the tube tocorrect length and then cutting the leading end at an angle ofapproximately 30 degrees relative to the plane normal to the axis. Thetubular blank is then coated, both interiorly and exteriorly, with asuitable lubricant such as a phosphate coating. The thus preparedtubular blank 66, as shown in FIGURE 3, is inserted in the bore 30 ofthe guide sleeve 28 with the short side aligned with the short side ofthe cavity 20. By means of the ram 64, the tubular blank 66 is forceddownwardly, and the lower end portion thereof is first moved through theconfined cylindrical space of generally annular cross section betweenthe wall of the bore 30 and the mandrel extension 38 and is then forcedthrough the confined elongated arcuate space of generally annular crosssection between the wall of the cavity and the mandrel 36 to theposition shown in FIGURE 4. As the lower end portion of the tubularblank 66 is forced through the cavity 20, the ring members 58 and 60 aresuccessively engaged and pushed outwardly of the cavity exit 24. In thismanner, the tubular blank 66 is formed with an elbow 68 at the end of atangent 70 to produce a long tangent elbow.

While the elbow 68 is being formed, the floating mandrel 36 and mandrelextension 38 prevent the walls of the tube blank 66 from collapsing andseek their own location to accommodate variations in wall thickness asbending occurs, the slight increase in the diameter of the cavity 20from the entrance 22 to the exit 24 accommodates movement of the lowerend of the tubular blank 66 therethrough, and the differential in theradii of curvatures of the centerlines of the cavity 20 and the mandrel36 allows for a differential in the wall thickness of the elbow 68 atthe crotch and back wall thereof. In the latter respect, the radialwidth on the short side of the arcuate space occupied by the crotch ofthe elbow is greater than the radial width on the long side of thearcuate space occupied by the back wall of the elbow. By reason of theuse of the floating mandrel 36 and mandrel extension 38, thinning of thewall areas of the elbow 68 is minimized, greater uniformity in wallthickness is attained, and the dilferential in wall thickness at thecrotch and back wall relative to the remaining wall areas is reduced.While the elbow 68 illustrated in FIGURE 4 is a 90 degree elbow, it willbe appreciated that the radius of curvature of the centerline of thecavity 20 may be varied to form elbows of different angles. Finally, theapparatus and method of the present invention is adapted for coldforming or producing long tangent elbows from tube blanks either offerrous or non-ferrous material.

After the elbow 68 has been formed, the ram 64 is retracted, the mandrelextension 38 is removed from the .4 top of the guide sleeve 28, and theyoke assembly 46 is removed from about the die 12. Then, a series ofballs, or any other suitable flexible pusher means, are inserted in thetangent 70 and forced, by any suitable pressure producing means, againstthe end of the mandrel 36 for pushing the latter out of the elbow 68 asindicated in dotted lines in FIGURE 4. Thereafter, the guide sleeve 28is removed from the die 12 and the die sections 16 and 18 are separatedso that the completed long tangent elbow may be removed. To prepare thedie assembly 10 for forming another long tangent elbow, the die sections16 and 18 are assembled together, the guide sleeve 28 is attached to thedie 12, the mandrel 36 and ring members 58 and 60 are inserted in thecavity 20, the yoke assembly 46 is clamped about the die 12, and themandrel extension 38 is inserted in the bore 30 of the guide sleeve 28.The die sections 16 and 18, the die extension 14, the horn 36, the hornextension 38, and the yoke assembly 46 may be arranged to be assembledand disassembled either manually or automatically.

While there has been shown and described a preferred embodiment of thepresent invention, it will be understood by those skilled in the artthat various rearrangements and modifications may be made thereinwithout departing from the spirit and scope of the invention.

What is claimed is:

1. For use in forming a long tangent elbow, the combination of a diehaving an arcuate cavity of circular cross section presenting anentrance and an exit, an arcuate mandrel of circular cross sectionfioatingly disposed in said cavity with one end terminating at saidentrance and with the other end extending outwardly of said exit,reaction means spaced from said die and being freely engaged incompression by said other end of said mandrel to position said mandrellengthwise of said cavity, and ring members arranged loosely in saidcavity about said mandrel for positioning the latter radially.

2. The combination of claim 1 wherein the radius of curvature of thecenterline of said mandrel is greater than the radius of curvature ofthe centerline of said cavity.

3. The combination of claim 2 wherein the diameter of said cavityincreases slightly from said entrance to said exit.

4. The combination of claim 3 including die extension means projectingfrom said die and formed with a cylindrical bore communicating at oneend with and having the same diameter as said entrance, and furtherincluding a cylindrical mandrel extension disposed in said bore andhaving one end engaging said one end of said arcuate mandrel.

5. The combination of claim 4 wherein said mandrel extension is allowedto swivel relative to said arcuate mandrel.

6. For use in forming a long tangent elbow, the combination of a diehaving an arcuate cavity of circular cross section presenting anentrance and an exit, an arcuate mandrel of circular cross sectionfloatingly disposed in said cavity with one end terminating at saidentrance and with the other end extending outwardly of said exit, theradius of curvature of the centerline of said arcuate mandrel beinggreater than the radius of curvature of the centerline of said cavity,ring members arranged loosely in said cavity about said arcuate mandrelfor positioning the latter radially, reaction means spaced from said dieand being freely engaged in compression by said other end of saidmandrel to position said mandrel lengthwise of said cavity, dieextension means projecting from said die and formed with a cylindricalbore communicating at one end with and having the same diameter as saidentrance, a cylindrical mandrel extension disposed in said bore andhaving one end engaging said one end of said arcuate mandrel, and saidmandrel extension being allowed to swivel relative to. Said arcuatemandrel.

7. The combination of claim 6 wherein said die is comprised of twosections having mating faces lying in the plane of the centerline ofsaid cavity, and wherein said die extension means is comprise of a guidesleeve secured to said die.

8. A method of forming a long tangent elbow comprising the steps ofmoving one end portion of a tubular blank lengthwise through acylindrical bore in a die assembly and over an interior cylindricalmandrel, forcing the tubular blank through an arcuate cavity in the dieassembly and over an arcuate mandrel positioned radially by ring memberswhich are pushed from the arcuate cavity as the tubular blank progressesthrough the latter whereby to form an elbow at one end of the tubularblank to produce a long tangent elbow, removing said cylindrical mandrelfrom the tangent of said long tangent elbow, removing said arcuatemandrel from said elbow, and removing said long tangent elbow from saiddie assembly.

References Cited UNITED STATES PATENTS 454,186 6/1891 Rosenfield 72-3435 1,908,373 5/1933 Loepsinger 29157 1,996,838 4/1935 Snell 723562,936,019 5/1960 Miller 72-343 FOREIGN PATENTS 10 48,289 6/1966 Germany.

RICHARD J. HERBST, Primary Examiner US. Cl. X,R. 15

